Facile Conversion of the Face-Centered Cubic Prussian-Blue Material K2[Mn2(CN)6] into the Spinel Oxide Mn3O4 at the Solid/Water Interface

The preparation of crystalline Mn3O4 via a new, mild solution method is described. The polymeric Prussian-blue-type starting material decomposes at room temperature in the presence of water to give a pure product in high yield. The oxide shows typical structural features of Mn3O4, but the magnetic properties are different from traditionally prepared samples, with coercive fields four times larger than that of Hausmannite (see Figure).